bron

bron

Tiny test runner for Node.js

• Single test() function, plus .skip() and .only()
• No magic, no implicit globals, no separate processes, no dependencies
• Use the Node.js built-in assert module, or bring your own (e.g. chai, should.js)
• Run tests in parallel (default), or serial
• Timeouts (default: 15s)
• Requires Node.js v12.20+
• Written in/published as pure ES Modules

Why?

Often for small projects, test suites consist of some wrapped assertions in test or it functions. Node.js has a fine assert module built-in, while exception output is pretty since Node v12. Last but not least, if any test fails, the process should exit with a non-zero code so that CI/CD environments can act accordingly.

Turns out this isn't very hard to implement, all source code of bron combined is only <100 LOC. In case you need more from your test framework, I'm happy to recommend one of the more full fledged options:

Runner	Dependencies	Size
Bron (v1.1.0)	0	5K
Tape (v4.11.0)	32	265K
Mocha (v6.2.0)	116	1.53M
Ava (v2.2.0)	387	3.68M

Not featuring...

• Extensive command-line options
• TAP reporting
• Fancy colors
• Setup/teardown helpers (e.g. beforeEach, after)
• Browser support

Installation

npm install bron -D

Add a test script to run the tests (npm test), e.g.:

{
  "scripts": {
    "test": "bron test/*.js"
  }
}

Usage from CLI

bron <file> [--serial] [--timeout=ms]

Writing tests

sync

import test from 'bron';
import { strict as assert } from 'assert';

const add = (x, y) => x + y;

test('should pass', () => {
  assert.equal(add(1, 2), 3);
});

test('should fail', () => {
  assert.equal(add(1, 2), 4);
});

$ bron test.js
✔ should pass
✖ should fail
AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:

3 !== 4

    at /Users/lars/Projects/bron/sync.js:11:10
    ...

✖ 1 test(s) failed
✔ 1 test(s) passed

async

No magic, but know that the tests run in parallel.

const isTwoAsync = x => (x === 2 ? Promise.resolve('OK') : Promise.reject('NOT OK'));

test('should pass with resolved promise', () => {
  assert.doesNotReject(() => isTwoAsync(2));
});

test('should pass with rejected promise', () => {
  assert.rejects(() => isTwoAsync(10), /NOT OK/);
});

serial

Add --serial:

const wait = milliseconds => new Promise(resolve => setTimeout(resolve, milliseconds));

test('should run serial (first)', async () => {
  await wait(100);
  assert(true);
});

test('should run serial (last)', async () => {
  await wait(0);
  assert(true);
});

$ bron --serial
✔ should run serial (first)
✔ should run serial (last)

promises

Return a promise, and the test will pass (resolved) or fail (rejected).

const isTwoAsync = x => (x === 2 ? Promise.resolve('OK') : Promise.reject('NOT OK'));

test('should pass with resolved promise', () => {
  return isTwoAsync(2);
});

test('should fail with rejected promise', () => {
  return isTwoAsync(10);
});

$ bron
✔ should pass with resolved promise
✖ should fail with rejected promise
NOT OK

✖ 1 test(s) failed.
✔ 1 test(s) passed.

.skip

test.skip('should be skipped', () => {
  assert.equal(1, 1);
});

.only

test.only('should pass', () => {
  assert.equal(1, 1);
});

test('should be skipped', () => {
  assert.equal(1, 1);
});

You can use .only multiple times (each .only will run).

Timeout

Add --timeout=n (with n in milliseconds) to change the default value for each test (15000).